In data storage, storage device mirroring replicates data stored on a primary data storage system to a secondary data storage system, in order to ensure redundancy. For a storage system comprising a pair of storage devices, mirroring can be implemented either synchronously or asynchronously. During synchronous mirroring, a host communicating with the storage system receives a write acknowledgement after data is successfully written to both of the mirrored storage devices. During asynchronous mirroring, the host receives the write acknowledgement after the data is written to a first of the mirrored storage devices, and the data can be written to a second of the mirrored storage devices at a later time.
Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.